Atomic Composition and Morphology of Thin Films of Resveratrol Deposited on Oxidized Silicon and Polycrystalline Gold Surfaces

Physics of the Solid State - The atomic composition of films of a polyphenol antioxidant, namely, resveratrol (RVL), with a thickness of up to 50 nm thermally deposited on an oxidized silicon...     

The Unoccupied Electronic States of the Ultrathin Diphenylphthalide Films on the Surface of the Highly Oriented Pyrolytic Graphite

Physics of the Solid State - The results of diagnostics of the atomic composition of a diphenylphthalide (DPP) film thermally precipitated in vacuum by the of X-ray photoelectric spectroscopy (XPS)...     

Structure of vacant electronic states of an oxidized germanium surface upon deposition of perylene tetracarboxylic dianhydride films

This paper presents the results of the investigation of the interface potential barrier and vacant electronic states in the energy range of 5 to 20 eV above the Fermi level (E_F) in the deposition of perylene tetracarboxylic dianhydride (PTCDA) films on the oxidized germanium surface ((GeO₂)Ge). The concentration of oxide on the (GeO₂)Ge surface was determined by X-ray photoelectron spectroscopy. In the experiments, we used the recording of the reflection of a test low-energy electron beam from the surface, implemented in the mode of total current spectroscopy. The theoretical analysis involves the calculation of the energy and spatial distribution of the orbitals of PTCDA molecules by the density functional theory (DFT) using B3LYP functional with the basis 6-31G(d), followed by the scaling of the calculated values of the orbital energy according to the procedure well-proven in the studies of small organic conjugated molecules. The pattern of changes in the fine structure of the total current spectra with increasing thickness of the PTCDA coating on the (GeO₂)Ge surface to 6 nm was studied. At energies below 9 eV above E_F, there is a maximum of the density of unoccupied electron states in the PTCDA film, formed mainly by π* molecular orbitals. The higher density maxima of unoccupied states are of σ* nature. The formation of the interface potential barrier in the deposition of PTCDA at the (GeO₂)Ge surface is accompanied by an increase in the work function of the surface, E_vac–E_F, from 4.6 ± 0.1 to 4.9 ± 0.1 eV. This occurs when the PTCDA coating thickness increases to 3 nm, and upon further deposition of PTCDA, the work function of the surface does not change, which corresponds to the model of formation of a limited polarization layer in the deposited organic film.     

Unoccupied Electron States of Ultrathin Quaterphenyl Films on the Surfaces of Layered CdS and Oxidized Silicon

Physics of the Solid State - Some results of studying the unoccupied electron states and the formation of a boundary potential barrier during the thermal vacuum deposition of ultrathin...     

Unoccupied Electronic States and Potential Barrier in Films of Substituted Diphenylphthalides on the Surface of Highly Ordered Pyrolytic Graphite

Physics of the Solid State - The results of a study of the unoccupied electronic states of ultrathin films of bis-carboxyphenyl-phthalide (DCA-DPP) and bis-methylphenyl-phthalide (DM-DPP) up to 8...     

Electronic structure of the conduction band of the interface region of ultrathin films of substituted perylenedicarboximides and the germanium oxide surface

The results of the investigation of the electronic structure of the conduction band and the interfacial potential barrier during the formation of interfaces of dioctyl-substituted perylenedicarboximide (PTCDI-C₈) and diphenyl-substituted perylenedicarboximide (PTCDI-Ph) ultrathin films with the oxidized germanium surface have been presented. The experimental results have been obtained using the very low energy electron diffraction (VLEED) technique in the total current spectroscopy (TCS) mode at energies in the range from 5 to 20 eV above the Fermi level E_F. The positions of the maxima of the fine structure of total current spectra (FSTCS) of the PTCDI-C₈ and PTCDI-Ph films differ significantly in the energy range from 9 to 20 eV above the Fermi level E_F, which can be associated with the difference between the substituents of the chosen molecules, dioctyl- and diphenyl-, respectively. At the same time, the positions of the lowenergy maxima in the FSTCS spectra at an energy 6–7 eV above the Fermi level E_F for the PTCDI-C₈ and PTCDI-Ph films almost coincide with each other. It has been suggested that these maxima are attributed to the electronic states of the perylene core of the molecules under investigation. The process of the formation of interfacial potential barriers of the PTCDI-C₈ and PTCDI-Ph films with the oxidized germanium surface has been analyzed. It has been found that the work functions of the surface, E_vac–E_F, differ little from 4.6 ± 0.1 eV over the entire range of organic coating thicknesses from 0 to 6 nm.